Nonvolatile nematic order manipulated by strain and magnetic field in a layered antiferromagnet

Electronic nematicity refers to a state whose electronic properties spontaneously break rotation symmetries of the host crystalline lattice, leading to anisotropic electronic properties. In this work, we demonstrate that the layered antiferromagnet CoTa3S6 exhibits a switchable nematic order, evidenced by the emergence of both resistivity anisotropy and optical birefringence. This nematic state sets in at a temperature T* distinct from that of the antiferromagnetic transitions in the system, indicating a separate symmetry-breaking mechanism. The nematic order can be manipulated either by an in-plane rotation symmetry-breaking strain or in-plane magnetic field, with the latter exhibiting a pronounced non-volatile memory effect. Remarkably, we find that the broken three-fold rotation symmetry in electronic transport is restored with a moderate out-of-plane field. We hypothesize that the nematicity is of electronic origin and emerges from instabilities associated with van Hove singularities. The resulting phase diagram points to an intertwined interplay between the electronic nematicity and the proposed underlying collinear and non-coplanar spin orders. Our findings establish CoTa3S6 as a versatile antiferromagnetic platform with highly tunable functionalities arising from the breaking of rotational, time-reversal, and inversion symmetries. CoTa3S6 is a layered chiral antiferromagnet consisting of planes of Cobalt atoms in a triangular lattice, between layers of TaS2. Here, Feng et al find that CoTa3S6 hosts a nematic order whose nematic director can be controllably switched via applied strain or in-plane magnetic fields.